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6
Summary of Results
T he study charge and approach and the main points from the preced-
ing chapters are summarized in this chapter. The discussion summa-
ries provide the basis for the findings presented at the end of the chapter.
RECAP OF STUDY CHARGE AND APPROACH
Section 16 of the Pipeline Safety, Regulatory Certainty, and Job Cre-
ation Act of 2011 calls for the Secretary of Transportation to âcomplete
a comprehensive review of hazardous liquid pipeline facility regulations
to determine whether the regulations are sufficient to regulate pipeline
facilities used for the transportation of diluted bitumen. In conduct-
ing the review, the Secretary shall conduct an analysis of whether any
increase in the risk of a release exists for pipeline facilities transporting
diluted bitumen.â1 A determination of release risk requires an assess-
ment of both the likelihood and the consequences of a release. To inform
its assessment of the former, the U.S. Department of Transportation
contracted with the National Research Council to convene an expert
committee to âanalyze whether transportation of diluted bitumen by
transmission pipeline has an increased likelihood of release compared
with pipeline transportation of other crude oils.â
As detailed in Chapter 1, the project statement of task calls for a two-
phase study, with the conduct of the second phase contingent on the
outcome of the first. In the first phase, the study committee was asked to
examine whether shipments of diluted bitumen can affect transmission
pipelines and their operations so as to increase the likelihood of release
â Public Law 112-90, enacted January 3, 2012.
1
99

100 Effects of Diluted Bitumen on Crude Oil Transmission Pipelines
when compared with shipments of other crude oils transported by
pipeline. In the potential second phaseâto be undertaken only if a find-
ing of increased likelihood of release is made in the firstâthe commit-
tee was asked to review federal pipeline safety regulations to determine
whether they are sufficient to mitigate an increased likelihood of release
from diluted bitumen. If the committee did not find an increased likeli-
hood of release, or the information available was insufficient to make a
finding, the committee was expected to prepare a final report document-
ing the study approach and results.
The committee reviewed data on reported pipeline releases. The
review provided insight into the general causes of pipeline failures,
but the incident records alone could not be used to determine whether
pipelines are more likely to fail when they transport diluted bitumen
than when they transport other crude oils. Having examined the general
causes of failures, the committee focused on the specific sources of pipe-
line damage that can be influenced by the transported crude oil. Specifi-
cally, it identified the chemical and physical properties of crude oil that
can cause or contribute to sources of pipeline failure from damage sus-
tained internally or externally or as a result of mechanical forces.
The committee did not perform its own testing of pipelines or crude
oil shipments. Information on the properties of shipments of diluted
bitumen and other crude oils was obtained from public websites and
assay sheets. Additional information was obtained from a review of gov-
ernment reports and technical literature, queries of oil producers and
pipeline operators, field visits, and inferences from secondary sources
such as the maximum water and sediment content for pipeline ship-
ments as specified in pipeline tariffs. The committee then compared the
relevant properties of shipments of diluted bitumen with the range of
properties observed in other crude oil shipments to identify instances
in which diluted bitumen fell outside or at an extreme end of the range.
In view of the possibility that some pipeline operators may modify
their operating and maintenance practices in transporting diluted bitu-
men, the committee first posited potential differences and then sought
evidence. Operators were questioned about their practices. The commit-
tee looked for indications of changes in standard procedures, including
corrosion control practices, that could inadvertently make pipelines
more susceptible to sources of failure.

Summary of Results 101
MAIN POINTS FROM CHAPTER DISCUSSIONS
Crude Oil Pipelines in the United States
As described in Chapter 2, the crude oil transmission network in the
United States consists of an interconnected set of pipeline systems.
Crude oil shipments traveling through the network often move from
one pipeline system to another and are sometimes stored at termi-
nals. Most operators of transmission systems are common carriers
who do not own the crude oil they transport but provide transporta-
tion services for a fee. Few major transmission pipelines are dedicated
to transporting specific grades or varieties of crude oil. They usually
move multiple batches of crude oil, often provided by different ship-
pers and encompassing a range of chemical and physical properties.
Crude oil shipments are treated to meet the quality requirements of
the pipeline operator as well as the content and quality demands of
the refinery customer.
Pipeline systems traverse different terrains and can vary in spe-
cific design features, components, and configurations. The differences
require that each operator tailor operating and maintenance strate-
gies to fit the circumstances of its systems in accordance with the
federal pipeline safety regulations. Nevertheless, the systems tend to
share many of the same basic components and follow similar operat-
ing and maintenance procedures. Together, regulatory and industry
standards, system connectivity, and economic demands compel both a
commonality of practice and a shared capability of handling different
crude oils.
Bitumen Properties, Production, and Transportation by Pipeline
As discussed in Chapter 3, the bitumen imported into the United States
is derived from Canadian oil sands. Canadian bitumen is both mined and
recovered in situ using thermally assisted techniques. A large share of the
bitumen deposits is too deep for mining, so in situ recovery accounts for
an increasing percentage of bitumen production. Because mined bitu-
men does not generally have qualities suitable for pipeline transporta-
tion and refinery feed, it is processed into synthetic crude oil in Canada.
Bitumen recovered in situ with thermally assisted methods has lower

102 Effects of Diluted Bitumen on Crude Oil Transmission Pipelines
water and sediment content and is thus better suited to long-distance
transportation by pipeline than is mined bitumen. Bitumen imported
into the United States is produced in situ through thermally assisted
methods rather than by mining.
Like all forms of petroleum, Canadian bitumen is a by-product of
decomposed organic materials and thus a mixture of many hydro-
carbons. The bitumen contains a relatively large concentration of
asphaltenes that contribute to its high density and viscosity. At ambient
temperatures, bitumen does not flow and must be diluted for transporta-
tion by unheated pipelines. Diluents consist of light oils, including natu-
ral gas condensate and light synthetic crude oils created from bitumen.
Although the diluents consist of low-molecular-weight hydrocarbons,
shipments of diluted bitumen do not contain a higher percentage of these
light hydrocarbons than do other crude oil shipments. The dilution pro-
cess yields a stable and fully mixed product for shipment by pipeline with
density and viscosity levels in the range of other crude oils transported
by pipeline in the United States.
Shipments of diluted bitumen are piped at operating temperatures,
flow rates, and pressure settings typical of crude oils with similar density
and viscosity levels. Shipment water and sediment content conforms to
the Canadian tariff limits, which are more restrictive than those in U.S.
pipeline tariffs. Solids in diluted bitumen shipments are comparable in
quantity and size with solids in other crude oil shipments transported
by pipeline. While the sulfur in diluted bitumen is at the high end of the
range for crude oils, it is bound with hydrocarbons and not a source of
corrosive hydrogen sulfide. Diluted bitumen has higher acid content
than many other crude oils, but the stable organic acids that raise acidity
levels are not corrosive at pipeline temperatures.
Review of Pipeline Incident Data
A logical step in addressing the question of whether shipments of diluted
bitumen have a greater propensity to cause pipeline releases than ship-
ments of other crude oils is to examine historical release records. The
incident statistics can be used to identify the general sources of pipe-
line failure. However, the information contained in the U.S. and Cana-
dian incident records is insufficient to draw definitive conclusions. As

Summary of Results 103
explained in Chapter 4, one reason is that the causal categories in the
databases lack the specificity needed to assess the particular ways in
which transporting diluted bitumen can affect the susceptibility of
pipelines to failure. Another reason is that incident records do not con-
tain information on the types of crude oil transported and the proper-
ties of past shipments in the affected pipeline. Because many pipeline
releases involve cumulative and time-dependent damage, there is no
practical way to trace the transportation history of a damaged pipeline
to assess the role played by each type of crude oil and its properties in
transport.
Incident reporting systems in Canada and the United States do not
have uniform reporting criteria and coverage. Given the relatively small
number of pipeline incidents, even minor variations in reporting crite-
ria can lead to significant differences in incident frequencies and causal
patterns. Some reporting systems combine incident reports from oil
gathering and transmission systems, while others do not. Variation
in reporting coverage is problematic because gathering pipelines are
fundamentally different from transmission pipelines in design, main-
tenance, and operations and in the quality and quantity of the liquids
they carry.
Assessing the Effects of Diluted Bitumen on Pipelines
The chemical and physical properties of diluted bitumen were exam-
ined in Chapter 5 to determine whether any differ sufficiently from
those of other crude oils to increase the likelihood of pipeline failures
from sources of damage internally or externally or from mechanical
forces. Any differences that could affect either the frequency or sever-
ity of the failure mechanism or the ability to mitigate a potential failure
mechanism would suggest a difference in failure likelihood. No proper-
ties were found to differ in any way that may change the likelihood of
pipeline damage and failure. An assessment was also made with regard
to whether pipeline operators transporting diluted bitumen alter their
operating and maintenance procedures in ways that can make pipelines
more prone to the causes of failure the procedures are intended to pre-
vent. No differences were found in these procedures. Summaries of the
assessments are presented in Box 6-1.

104 Effects of Diluted Bitumen on Crude Oil Transmission Pipelines
box 6-1
Summary of Assessments of the Effects of Diluted Bitumen
on Causes of Pipeline Damage
Internal Degradation
A review of product properties pertaining to internal pipeline corrosion
and erosion did not find that shipments of diluted bitumen are any more
likely than shipments of other crude oils to cause these failure mechanisms.
Shipments of diluted bitumen do not contain unusually high levels of water,
sediment, dissolved gases, or other agents that can cause internal corrosion.
The organic acids contained in diluted bitumen are not corrosive to steel
at pipeline temperatures. The densities and viscosities of diluted bitumen
shipments are within the range of other crude oils, and the velocity and tur-
bulence with which shipments flow through pipelines are comparable and
limit the formation of corrosive deposits. On the basis of an examination of
the factors that influence microbial growth, diluted bitumen does not have
a higher likelihood than other crude oils of causing microbiologically influ-
enced corrosion. Because shipments of diluted bitumen have solids content
and flow regimes comparable with those of other crude oil shipments, they
do not differ in their propensity to cause erosion of transmission pipelines.
External Degradation
Pipelines can sustain external damage from corrosion and cracking. Because
diluted bitumen only contacts the inside of a pipeline, it can contribute to
external degradation only as a result of changes in pipeline operational
parameters, specifically pipeline temperature and pressure levels. Elevated
operating temperatures can increase the likelihood of external corrosion
and cracking by causing or contributing to the degradation of protective
coatings and by accelerating rates of certain degradation mechanisms. Ele-
vated operating pressures can cause stress loadings and concentrations that
lead to stress-related cracking, particularly at sites of corrosion and preex-
isting damage. Because the densities and viscosities of diluted bitumen are
comparable with those of other crude oils, it is transported at comparable
operating pressures and temperatures. For this reason, the likelihood of
temperature- and pressure-related effects is indistinguishable for diluted
bitumen and other crude oils of similar density and viscosity. Consequently,
diluted bitumen will not create a higher propensity for external corrosion
and cracking in transmission pipelines.
(continued)

Summary of Results 105
box 6-1 (continued)
Mechanical Damage
Mechanical damage to the pipeline and its components can occur as a result of
overpressurization or outside forces. Mechanical forces can cause an imme-
diate release or make the pipeline more susceptible to release by destabiliz-
ing support structures; damaging other components such as valves and joints;
and weakening resistance to other failure mechanisms, such as corrosion
attack. The study examined several possible causes of an increased potential
for mechanical damage due to the properties of the transported liquid, includ-
ing the potential for shipments of diluted bitumen to cause pressure surges or
to interact with outside forces that can cause damage in pipelines. None of the
properties or operating parameters of diluted bitumen shipments was found
to be sufficiently different from those of other crude oils to suggest a higher
potential to cause or exacerbate mechanical damage in pipelines.
Effects on Operations and Maintenance Procedures
As common carriers, operators of transmission pipelines generally have the
ability to transport the wide range of crude oil varieties that are in the com-
mercial stream. Accordingly, operations and maintenance procedures are
designed to be robust, capable of ensuring operational reliability and safety
without the need for procedural modifications from one crude oil shipment
to the next. The chemical and physical properties of diluted bitumen ship-
ments do not suggest that transporting them by pipeline requires opera-
tions and maintenance procedures that differ from those of other crude oil
shipments having similar properties. Likewise, inquiries with operators and
searches of industry guidelines and advisories did not indicate any specific
issues associated with transporting diluted bitumen that would negatively
affect operators as they carry out their standard operations and maintenance
programs, including their corrosion detection and control capabilities.
STUDY RESULTS
Central Findings
The committee does not find any causes of pipeline failure unique to the
transportation of diluted bitumen. Furthermore, the committee does not
find evidence of chemical or physical properties of diluted bitumen that are

106 Effects of Diluted Bitumen on Crude Oil Transmission Pipelines
outside the range of other crude oils or any other aspect of its transportation
by transmission pipeline that would make diluted bitumen more likely than
other crude oils to cause releases.
Specific Findings
Diluted bitumen does not have unique or extreme properties that make it
more likely than other crude oils to cause internal damage to transmis-
sion pipelines from corrosion or erosion. Diluted bitumen has density and
viscosity ranges comparable with those of other crude oils. It is moved
through pipelines in a manner similar to other crude oils with respect
to flow rate, pressure, and operating temperature. The amount and size
of solid particles in diluted bitumen are within the range of other crude
oils so as not to create an increased propensity for deposition or erosion.
Shipments of diluted bitumen do not contain higher concentrations of
water, sediment, dissolved gases, or other agents that cause or exacer-
bate internal corrosion, including microbiologically influenced corro-
sion. The organic acids in diluted bitumen are not corrosive to steel at
pipeline operating temperatures.
Diluted bitumen does not have properties that make it more likely than
other crude oils to cause damage to transmission pipelines from exter-
nal corrosion and cracking or from mechanical forces. The contents of a
pipeline can contribute to external corrosion and cracking by causing
or necessitating operations that raise the temperature of a pipeline,
produce higher internal pressures, or cause more fluctuation in pres-
sure. There is no evidence that operating temperatures and pressures
are higher or more likely to fluctuate when pipelines transport diluted
bitumen than when they transport other crude oils of similar density and
viscosity. Furthermore, the transportation of diluted bitumen does not
differ from that of other crude oils in ways that can lead to conditions
that cause mechanical damage to pipelines.
Pipeline operating and maintenance practices are the same for ship-
ments of diluted bitumen and shipments of other crude oils. Operating and
maintenance practices are designed to accommodate the range of crude
oils in transportation. The study did not find evidence indicating that
pipeline operators change or would be expected to change such practices
while transporting diluted bitumen.

Summary of Results 107
These study results do not suggest that diluted bitumen will experi-
ence pipeline releases at a rate that is higher than its proportion of the
crude oil stream. Future pipeline releases can be expected to occur, and
some will involve diluted bitumen. All pipeline releases can be conse-
quential. As explained at the outset of this report, the committee was
not asked or constituted to study whether pipeline releases of diluted
bitumen and other crude oils differ in their consequences or to deter-
mine whether such a study is warranted. Accordingly, the report does
not address these questions and should not be construed as having
answered them.

TRB Special Report 311: Effects of Diluted Bitumen on Crude Oil Transmission Pipelines analyzes whether shipments of diluted bitumen have a greater likelihood of release from pipelines than shipments of other crude oils. The oil sands region of Canada is the source of diluted bitumen shipped by pipeline to the United States.

The committee that produced the report did not find any pipeline failures unique to the transportation of diluted bitumen or evidence of physical or chemical properties of diluted bitumen shipments that are outside the range of those of other crude oil shipments. The committee's comprehensive review did not find evidence of any specific aspect of the transportation of diluted bitumen that would make it more likely than other crude oils to cause pipeline releases.

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